Gas-Phase Oxidation of Alcohols: Innovation in Industrial Technologies and Recent Developments - Transition Metal Catalysis in Aerobic Alcohol Oxidation - page 224

Antoniadou et al. 133 studied the photocatalytic oxidation of ethanol over Ru-
doped TiO 2 in three different ways: oxidation in the gas phase (100 1C,
ethanol:oxygen = 1:2), reforming in the aqueous phase and as a fuel in a
photoactivated fuel cell. They found that in the first case (which is the one of
interest here), the conversion and selectivity towards acetaldehyde increased
with increase in the amount of dopant but only up to a certain point, after
which it started to decrease again (reaching a maximum of 97% selectivity at
55% of conversion over RuO 2 /TiO 2 loaded at 0.3 wt%). From this trend, they
concluded that the overall photoactivity depends on the availability of
adsorption sites on the catalyst, i.e. the TiO 2 not covered by the RuO x , while
the Ru species play an essential role in addressing the selectivity to
acetaldehyde, thus making it necessary to find an adequate balance in
composition. In other studies performed by the same research team,
different catalysts were tested including Au/TiO 2 134 (82% conversion and
95% selectivity at 60 1C), Pt/TiO 2 135 (85% conversion and 90% selectivity at
60 1C) and VO x /TiO 2 136 (66% conversion and 99% selectivity at 60 1C) in the
presence of blue phosphors, but, up to now, the best results they obtained
were with RuO x -VO x /TiO 2 137 (100% conversion and selectivity at 100 1C).

d n 4 r 4 n g | 3

8.6 Conclusion
The gas-phase oxidation of alcohols - a reaction known and industrially
applied for many years - is still the subject of intense investigation, with the
aim of finding more active, selective and stable catalysts both for industrial
methanol oxidative dehydrogenation and higher alcohol oxidation, espe-
cially in the case of ethanol, which is now the subject of renewed interest as a
bioplatform molecule. The literature on this topic is mainly focused on the
catalyst properties needed to obtain high selectivity either to acetaldehyde or
to acetic acid, with interest also in the synthesis of dimerization molecules
such as ethyl acetate or condensation compounds. Also in this field, as in
many others, the majority of studies reported in the literature have been
focused on catalysts based on supported Au nanoparticles. New products
based on biomolecules, new technology for old reactions and improved
catalysts for already established processes are all fields with scientific,
technical and economic opportunities included in the vision of a more
sustainable chemical industry based on biomass as feedstock.

.

References
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